Rear subframe structure

ABSTRACT

A rear subframe structure is provided with a rear subframe configured such that a front cross member, a rear cross member, a pair of left and right upper side members, and a pair of left and right lower side members are connected; and a vehicle-body mounting portion formed. The rear subframe further includes a lower-arm support portion. The front cross member has a closed section, and a front portion of the closed section extends downwardly by forward and downward inclination of a left lateral portion and a right lateral portion of the front cross member. The lower-arm support portion is formed on a lower rear portion of the left lateral portion and the right lateral portion of the front cross member. The upper side member is connected to an upper rear portion of the left lateral portion and the right lateral portion of the front cross member.

TECHNICAL FIELD

The present invention relates to a rear subframe structure of a vehicle,and more particularly, to a rear subframe structure provided with a rearsubframe configured such that a front cross member extending in avehicle width direction, a rear cross member extending in the vehiclewidth direction on the rear side of the front cross member, a pair ofleft and right upper side members extending in a vehicle front-reardirection, and a pair of left and right lower side members extending inthe vehicle front-rear direction are connected in a substantially gridpattern in a plan view of a vehicle; and a vehicle-body mounting portionformed on each of both ends of the front cross member in the vehiclewidth direction, and on each of rear ends of the upper side members.

BACKGROUND ART

Generally, in an integral type suspension provided with an integral linkfor controlling a swing trajectory of a rear wheel in a side view whenthe rear wheel moves up and down (a so-called recession angle,specifically, an angle defined by a road surface, and a trajectory of arear wheel when the rear wheel moves up and down in a case where therear wheel rides on a step), all the load in a vehicle front-reardirection is exerted on a rear subframe because a trailing link is notprovided. In view of the above, generally, an H-shaped lower arm isprovided as a lower arm in order to secure rigidity of the rearsubframe.

On the other hand, in order to secure comfort of a passenger on a rearseat and to secure a low hip point, there is a demand for lowering theheight of a rear seat pan. As a result, an installation space of a rearsubframe tends to be narrowed from constraints on the layout withrespect to a rear seat pan, or the like. It is difficult to support thelower arm, and to linearly extend a front cross member or a side crossmember of a closed sectional structure with respect to a vehicle bodysupport portion of a rear subframe.

Specifically, in a configuration, in which a rear subframe is disposedin a narrow space of a lower portion of a rear seat pan where it isimpossible to connect a front cross member and a side member, whilesecuring a sufficient closed sectional structure, it is difficult tosecure high rigidity in the vehicle width direction, while securing aspace for a lower-arm support portion.

Patent Literature 1 discloses an integral-type rear suspension. In aconventional structure disclosed in Patent Literature 1, a front-sidearm support portion of an H-shaped lower arm projects downwardly from afront portion of a side member, and it may be difficult to providesufficient rigidity in the vehicle width direction. There is room forimprovement from an aspect of miniaturization and enhancing rigidity.

Further, Patent Literature 2 discloses a configuration, in which apanel-type side member constituting a rear subframe is provided, and aslant portion inclined from a front end of a portion of the side memberextending in a vehicle front-rear direction obliquely outwardly andobliquely downwardly toward the front side to a front-side vehicle-bodymounting portion is formed.

However, in Patent Literature 2, there is no detailed disclosure aboutan arm support portion of a lower arm.

CITATION LIST Patent Literature

Patent Literature 1: Specification of European Patent No. 1937498

Patent Literature 2: Specification of German Unexamined PatentPublication No. 3927987

SUMMARY OF INVENTION

An object of the present invention is to provide a rear subframestructure which enables to secure high rigidity in a vehicle widthdirection, while securing a space for a lower-arm support portion, in acase where a rear subframe is disposed in a narrow space of a lowerportion of a rear seat pan where it is impossible to connect a frontcross member and a side member, while securing a sufficient closedsectional structure.

An aspect of the present invention is directed to a rear subframestructure provided with a rear subframe configured such that a frontcross member extending in a vehicle width direction, a rear cross memberextending in the vehicle width direction on a rear side of the frontcross member, a pair of left and right upper side members extending in avehicle front-rear direction, and a pair of left and right lower sidemembers extending in the vehicle front-rear direction are connected in asubstantially grid pattern in a plan view of a vehicle; a vehicle-bodymounting portion formed on each of both ends of the front cross memberin the vehicle width direction, and on each of rear ends of the upperside members; and a lower-arm support portion for supporting a lowerarm. The front cross member has a closed section extending in thevehicle width direction, and a front portion of the closed sectionextends downwardly by forward and downward inclination of a left lateralportion and a right lateral portion of the front cross member. Thelower-arm support portion is formed on a lower rear portion of a leftlateral portion and a right lateral portion of the front cross member.The upper side member is connected to an upper rear portion of the leftlateral portion and the right lateral portion of the front cross member.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a perspective view of a rear subframe structure according tothe present invention;

FIG. 2 is a plan view of the rear subframe structure;

FIG. 3 is a bottom view of the rear subframe structure;

FIG. 4 is a front view of the rear subframe structure;

FIG. 5 is a rear view of the rear subframe structure;

FIG. 6 is a perspective view of the rear subframe structure when viewedfrom rear on a vehicle left side;

FIG. 7 is a perspective view of the rear subframe structure when viewedfrom rear and above on a vehicle right side;

FIG. 8A is a sectional view taken along the line A-A in FIG. 2;

FIG. 8B is a sectional view taken alone the line B-B in FIG. 2;

FIG. 9 is a sectional view taken along the line C-C in FIG. 2;

FIG. 10 is a side view illustrating essential parts of FIG. 2;

FIG. 11 is a sectional view taken along the line D-D in FIG. 10;

FIG. 12A is a plan view of a partition member;

FIG. 12B is a perspective view of the partition member;

FIG. 13A is a perspective view of a stabilizer support member; and

FIG. 13B is a front view of a brace.

DESCRIPTION OF EMBODIMENTS

In the following, an embodiment of the present invention is described indetail based on the drawings.

FIG. 1 is a perspective view of a rear subframe structure, FIG. 2 is aplan view of the rear subframe structure, FIG. 3 is a bottom view of therear subframe structure, FIG. 4 is a front view of the rear subframestructure, and FIG. 5 is a rear view of the rear subframe structure. InFIG. 1, the arrow F indicates a vehicle front side, the arrow Rindicates a vehicle rear side, the arrow IN indicates an inner side in avehicle width direction, and the arrow OUT indicates an outer side in avehicle width direction (the same definition is also applied to theother drawings).

Referring to FIG. 1 to FIG. 5, a rear subframe 10 for supporting a rearsuspension includes a front cross member 11 extending in the vehiclewidth direction, a rear cross member 12 extending in the vehicle widthdirection on the rear side of the front cross member 11, a pair of upperside members 13 and 13 (hereinafter, briefly referred to as upper sidemembers 13) for connecting the front cross member 11 and the rear crossmember 12 in a vehicle front-rear direction, and a pair of lower sidemembers 14 and 14 (hereinafter, briefly referred to as lower sidemembers) for connecting the front cross member 11 and the rear crossmember 12 in the vehicle front-rear direction. These members areconnected substantially in a grid pattern in a plan view of a vehicle.Each of the members 11 to 14 has a closed sectional structure.

In the embodiment, the upper side member 13 is connected to a lateralportion of the front cross member 11 in the vehicle width direction viaa pillar portion 33 to be described later, and extends from theconnection portion rearwardly of a vehicle. Further, the rear crossmember 12 connects rear portions of the paired left and right upper sidemembers 13 and 13 in the vehicle width direction, connects rear portionsof the paired left and right lower side members 14 and 14 in the vehiclewidth direction, and further connects the upper and lower side members13 and 14 in an up-down direction.

As illustrated in FIG. 2, the lower side member 14 is located on theinner side than the upper side member 13 in the vehicle width direction,and connects a lower portion of the front cross member 11 and a lowerportion of the rear cross member 12 in the vehicle front-rear direction.

As illustrated in FIG. 2 and FIG. 3, a distance between rear ends of thepaired left and right lower side members 14 and 14 is set smaller than adistance between front ends of the paired left and right lower sidemembers 14 and 14. Thereby, lower-arm rear-side support portions 12 band 12 c (see FIG. 6) to be described later are formed at positionswhere the lower-arm rear-side support portions 12 b and 12 c overlap theupper side member 13 in a plan view.

As illustrated in FIG. 1 to FIG. 5, front-side vehicle-body mountingportions 15 and 15 are formed on both ends of the front cross member 11in the vehicle width direction. A rear portion of the upper side member13 is smoothly formed into a curve rearwardly of a vehicle and outwardlyin the vehicle width direction. Rear-side vehicle-body mounting portions16 and 16 are formed on rear ends of the upper side members 13 and 13.The rear subframe 10 is mounted to a vehicle body, specifically, to arear side frame via the vehicle-body mounting portions 15 and 16.

The reference numeral 17 denotes a lower arm. A link support portion 17a is formed on a front portion of an outer end of the lower arm 17 inthe vehicle width direction. A lower end of an integral link 18 ispivotally supported on the link support portion 17 a. An upper end ofthe integral link 18 is pivotally connected to an integral link supportportion of a hub support 19. The integral link 18 is a link forcontrolling a swing trajectory (so-called recession angle) of a rearwheel in a side view when the rear wheel moves up and down.

In the embodiment, an H-shaped lower arm is employed as the lower arm17. A connection portion 17 b is formed on a rear portion of an outerend of the lower arm 17 in the vehicle width direction. The connectionportion 17 b is pivotally connected to a lower-arm support portion ofthe hub support 19.

The reference numeral 20 denotes a toe control link for setting a rearwheel to toe-in so as to secure wheel straightness. A connection portion20 a is formed on an outer end of the toe control link 20 in the vehiclewidth direction. The connection portion 20 a is pivotally connected to atoe control link support portion of the hub support 19.

The reference numeral 21 denotes an upper arm. A connection portion 21 ais formed on an outer end of the upper arm 21 in the vehicle widthdirection. The connection portion 20 a is pivotally connected to anupper-arm support portion of the hub support 19. In the embodiment, anI-shaped upper arm is employed as the upper arm 21.

As illustrated in FIG. 1, FIG. 4, and FIG. 5, a damper support portion19 a is integrally formed on the hub support 19. A damper 22 of a strutstructure is mounted on the damper support portion 19 a.

As illustrated in FIG. 2 and FIG. 3, a bulging portion 17 c bulgingrearwardly is formed on a rear portion of the lower arm 17. A coilspring 24 is wound between a spring lower retainer 23 mounted on anupper portion of the bulging portion 17 c, and a spring upper retainer(not illustrated) provided on the rear side frame on the vehicle bodyside.

As illustrated in FIG. 2, FIG. 3, and FIG. 5, a stabilizer 25 isprovided on the rear side of the rear cross member 12 along the rearcross member 12. The stabilizer 25 is formed into a bent shape forwardlyof a vehicle in such a manner that left and right ends of the stabilizer25 are located above the lower arm 17. The bent ends of the stabilizer25 are connected to the lower arm 17 by using a connection member. Thestabilizer 25 is configured to suppress a roll angle when one wheel isbumped or rebound by torsional rigidity resistance.

As illustrated in FIG. 4, a tunnel portion 11 a for receiving apropeller shaft 26 is formed in the middle of a lower portion of thefront cross member 11. The front cross member 11 is formed into a saddleshape. Further, a brace 27 as a reinforcement member for connectinglower portions of the tunnel portions 11 a in the vehicle widthdirection is provided.

As illustrated in FIG. 1 to FIG. 3, a differential mount portion 12 a isformed on an intermediate portion of the rear cross member 12 in thevehicle width direction. A differential mount bracket 29 is mounted onthe differential mount portion 12 a via a differential mount bush 28.

A vehicle in the embodiment is a vehicle of a type such that a drivingforce is transmitted to rear wheels. The vehicle is configured such thata rear portion of a rear differential device (not illustrated) issupported by the differential mount bracket 29.

FIG. 6 is a perspective view of the rear subframe structure when viewedfrom rear on a vehicle left side, FIG. 7 is a perspective view of therear subframe structure when viewed from rear and above on a vehicleright side, FIG. 8A is a sectional view taken along the line A-A in FIG.2, FIG. 8B is a sectional view taken along the line B-B in FIG. 2, FIG.9 is a sectional view taken along the line C-C in FIG. 2, FIG. 10 is aside view illustrating essential parts of FIG. 2, and FIG. 11 is asectional view taken along the line D-D in FIG. 10.

FIG. 6 to FIG. 11 illustrate a configuration of a vehicle left sideportion. The configuration of a vehicle right side portion issymmetrical or substantially symmetrical with respect to theconfiguration of the vehicle left side portion in a left-rightdirection.

As illustrated in FIG. 8A, FIG. 8B, FIG. 9, and FIG. 11, the front crossmember 11 has a structure such that a front panel 31 and a rear panel 32are joined and fixed, and has a closed section S1 (corresponding to afirst closed section of the present invention) extending in the vehiclewidth direction. Specifically, the closed section 51 is constituted bythe rear panel 32 on the middle side of the rear subframe 10, and thefront panel 31 including an upper surface 31 a extending rearwardly thanthe rear panel 32 and including a front surface 31 b extendingdownwardly than the rear panel 32.

As illustrated in FIG. 1 and FIG. 6, left and right lateral portions ofthe front cross member 11 are inclined forwardly and downwardly.Thereby, as illustrated in FIG. 8B and FIG. 9, a front portion of theclosed section 51 extends downwardly to form an enlarged closed sectionS1 a. Further, as illustrated in FIG. 8B and FIG. 9, a rear portion ofthe closed section S1 on a lateral portion of the front cross member 11is projected upwardly and forwardly to form a recessed closed section S1b (corresponding to a recessed portion of the present invention). Theenlarged closed section S1 a and the recessed closed section S1 b arecontinued.

As illustrated in FIG. 6, FIG. 8B, and FIG. 9, there is formed, on arear portion of the enlarged closed section S1 a, a lower-arm supportportion 32 a for supporting a front mounting portion 17 d out of frontand rear mounting portions 17 d and 17 e of the lower arm 17.

As illustrated in FIG. 8B, the upper side member 13 is connected to arear surface of an upper portion of the closed section S1, specifically,to a rear surface of the recessed closed section S1 b via the pillarportion 33.

As described above, by inclining a lateral portion of the front crossmember 11 in the vehicle width direction forwardly and downwardly, it ispossible to enlarge a front portion of the closed section S1 downwardly(see the enlarged closed section Sla) to secure rigidity in the vehiclewidth direction, while avoiding interference with a rear seat pan (arear floor panel), whereby rigidity in the vehicle width direction issecured without narrowing a swing range of the lower arm 17.

In other words, even in a structure configured such that the rearsubframe 10 is disposed in a narrow space of a lower portion of a rearseat pan where it is not possible to connect the front cross member 11and the upper side member 13, while securing a sufficient closedsectional structure (a linearly extending closed sectional structure),it is possible to secure high rigidity in the vehicle width direction,and to secure a space for the lower-arm support portion 32 a(specifically, secure a space for the mounting portion 17 d of the lowerarm 17).

As illustrated in FIG. 6, FIG. 7, and FIG. 8B, the pillar portion 33 hasa shape of a closed section S2 constituted by a rear plate 34 includingan upper-arm support portion 34 a for supporting a mounting portion 21 b(see FIG. 2) of the upper arm 21, and a front plate 35 (corresponding toa vertical wall portion of the present invention) including a lower-armsupport portion 35 a. As illustrated in FIG. 6 and FIG. 11, the rearplate 34 is formed to have a U-shaped section in a plan view.

As illustrated in FIG. 7, the front plate 35 includes a dome-shapedflange portion 35 b which extends from an outer peripheral edge of amain surface portion thereof forwardly of the vehicle, and which isabutted against a back surface of the rear panel 32 of the front crossmember 11 and welded.

As illustrated in FIG. 8B and FIG. 9, a second closed section S3(corresponding to a second closed section of the present invention)extending in the vehicle width direction is constituted by the closedsection S1 of a lateral portion of the front cross member 11 in thevehicle width direction, the front plate 35 located immediately on therear side of the closed section S1, and an upper surface of the lowerside member 14. Thereby, a space for supporting a lower arm is secured,and connection rigidity of the lower side member 14 is enhanced.

As illustrated in FIG. 7, a lower portion of the front plate 35 is fixedby abutment against an upper surface of the lower side member 14 andagainst an outer lateral surface of the lower side member 14 in thevehicle width direction and by welding.

As illustrated in FIG. 8B, the pillar portion 33 having a structure ofthe closed section S2 is formed immediately on the rear side of thesecond closed section S3. The pillar portion 33 includes the front plate35, extends upwardly from the lower side member 14, and is connected toa back surface of the front cross member 11. A rear surface of an upperportion of the pillar portion 33, specifically, a rear surface of anupper portion of the rear plate 34 is connected to a front portion ofthe upper side member 13 by welding.

In other words, the front-side lower-arm support portion 32 a out of thelower-arm support portions 32 a and 35 a is formed by a part (a part ofthe enlarged closed section S1 a) configured such that a front portionof the closed section Si extends downwardly out of a lateral portion ofthe front cross member 11 in the vehicle width direction, and therear-side lower-arm support portion 35 a is formed by the pillar portion33 having a structure of the closed section S2. Further, the pillarportion 33 is connected to all of the upper side member 13, the lowerside member 14, and the front cross member 11. According to thisconfiguration, it is possible to distribute load to be input via thelower-arm support portions 32 a and 35 a, and to attain high rigidity ofthe rear subframe 10.

Further, in order to secure a sufficient space for supporting a lowerarm while lowering a lateral portion of the front cross member 11 in thevehicle width direction, the pillar portion 33 (specifically, the rearplate 34) is used as a set plate, while reducing the size of therecessed closed section S1 b in the up-down direction than the size ofthe upper side member 13 in the up-down direction, whereby connectionrigidity is enhanced.

As illustrated in FIG. 6, FIG. 7, and FIG. 8B, the vertical-wall-shapedpillar portion 33 constituted by the front plate 35 and the rear plate34, and extending in the vehicle width direction and in the up-downdirection is held and fixed between a lateral portion of the front crossmember 11 in the vehicle width direction, and a front end of the upperside member 13.

As illustrated in FIG. 6, FIG. 7, and FIG. 8B, a lower portion of thepillar portion 33, specifically, lower portions of the front plate 35and the rear plate 34 are respectively connected to an upper surface ofthe lower side member 14 and to an outer lateral surface of the lowerside member 14 in the vehicle width direction. The upper-arm supportportion 34 a is formed on an upper portion of the rear plate 34, and thelower-arm support portion 35 a is formed on a lower portion of the frontplate 35.

According to the aforementioned configuration, load input from the upperand lower arms (the lower arm 17 and the upper arm 21) is directlytransmitted to the upper and lower side members 13 and 14 and to thefront cross member 11 for load distribution, whereby high rigidity ofthe rear subframe 10 is attained. Further, the upper-arm support portion34 a and the lower-arm support portion 35 a are formed on the pillarportion 33. This makes it possible to enhance positioning accuracy ofthe arms 17 and 21.

As illustrated in FIG. 6, FIG. 7, and FIG. 10, the upper-arm supportportion 34 a includes a substantially Z-shaped upper-arm support bracket36 on a rear portion thereof in a side view.

The upper-arm support bracket 36 includes a vertical piece 36 aextending in the up-down direction, an upper piece 36 b extendingrearwardly from an upper end of the vertical piece 36 a, and a lowerpiece 36 c extending forwardly from a lower end of the vertical piece 36a. The upper-arm support bracket 36 is integrally formed by these pieces36 a to 36 c. An upper half of the vertical piece 36 a and the upperpiece 36 b are abutted against an outer lateral surface of the upperside member 13 in the vehicle width direction and welded, and a frontend of the lower piece 36 c is abutted against a back surface of therear plate 34 and welded.

As illustrated in FIG. 10, the upper-arm support bracket 36 holds thepillar portion 33 in cooperation with the front cross member 11.Further, a front portion of the upper side member 13 and the pillarportion 33 are connected by the upper-arm support bracket 36. By theaforementioned holding structure of the pillar portion 33 by theupper-arm support bracket 36 and the front cross member 11, the pillarportion 33 is securely supported, and the upper arm 21 is supported bythe upper-arm support portion 34 a on the upper portion of the pillarportion 33 and the upper-arm support bracket 36, whereby supportrigidity of the upper arm 21 is enhanced. Further, connection rigiditybetween the pillar portion 33 and the upper side member 13 is enhanced.

As illustrated in FIG. 8B, an upper portion of the rear plate 34 of thepillar portion 33 is directly connected to the front cross member 11(specifically, a rear portion of the upper surface 31 a of the frontpanel 31), and the lower-arm support portions 35 a and 32 a areconstituted by a lower portion of the front plate 35 and a lower portionof the front cross member 11 (specifically, a lower portion of the rearpanel 32). Thus, load from the upper arm 21 and the lower arm 17 istransmitted to the front cross member 11 and to the upper and lower sidemembers 13 and 14 for load distribution, and high rigidity of the rearsubframe 10 is attained.

As illustrated in FIG. 8B and FIG. 10, the pillar portion 33 extendsbetween the upper side member 13 and the lower side member 14, and thelower-arm support portion 35 a is formed on a front surface of thepillar portion 33 on an upper side of the lower side member 14, in otherwords, on the front plate 35.

Further, as illustrated in FIG. 6, FIG. 7, and FIG. 8B, a toe controllink support portion 34 b is formed on a rear surface of the pillarportion 33 located below the lower-arm support portion 35 a, and on anouter lateral side of the lower side member 14 in the vehicle widthdirection, in other words, on the rear plate 34.

As illustrated in FIG. 6, FIG. 7, and FIG. 11, a toe control linksupport bracket 37 (hereinafter, simply referred to as a link supportbracket) for supporting the toe control link support portion 34 b fromthe rear side is provided on the rear subframe 10.

As illustrated in FIG. 6, FIG. 7, and FIG. 11, the link support bracket37 includes a front piece 37 a fixed upright on an upper surface of thelower side member 14 and extending in the vehicle front-rear direction,and a lateral piece 37 c extending from a rear end of the front piece 37a outwardly in the vehicle width direction. The link support bracket 37is integrally formed by these pieces 37 a and 37 b. A horizontallyU-shaped cutaway portion 37 b is formed in the lateral piece 37 c. Thecutaway portion 37 b of the lateral piece 37 c is welded and fixed to anupper surface, an outer lateral surface, and a lower surface of thelower side member 14.

Further, the link support bracket 37 is mounted between the lower sidemember 14 and a back surface of the lower-arm support portion 35 a ofthe pillar portion 33.

The lower-arm support portion 35 a and the toe control link supportportion 34 b are displaced in the up-down direction. Thereby, a compactand dense layout by the support portions 35 a and 34 b, the lower arm17, and the toe control link 20 is obtained. Further, load from thelower arm 17 and the toe control link 20 is distributed to an uppersurface and a lateral surface of the lower side member 14, and furtherto the upper and lower side members 13 and 14, whereby high rigidity ofthe rear subframe 10 is attained. In addition to the above, the pillarportion 33 supports two components i.e. the lower arm 17 and the toecontrol link 20 to enhance positioning accuracy between the lower arm 17and the toe control link 20.

The lower-arm support portion 35 a for supporting the lower arm 17 isformed as a first arm support portion. Therefore, it is possible tooffset the front mounting portion 17 d of the lower arm 17 to the innerside in the vehicle width direction than an outer lateral edge of thelower side member 14 in the vehicle width direction. Thus, it ispossible to enhance freedom in setting an imaginary first arm swingcenterline L (in other words, a lower arm swing centerline) illustratedin FIG. 8B.

As illustrated in FIG. 8B, the mounting portions 17 d and 17 e areformed on front and rear portions of the lower arm 17 to be supported bythe lower-arm support portion 35 a. Specifically, the lower arm 17includes the front mounting portion 17 d on the front side with respectto the pivot center of the lower arm 17, and the rear mounting portion17 e on the rear side with respect to the pivot center of the lower arm17.

Further, the lower-arm rear-side support portions 12 b and 12 cconnected to the rear cross member 12 or integrally formed with the rearcross member 12 are formed such that the first arm swing centerline Llocated on the lower side than the lower-arm support portion 35 a of thepillar portion 33 and passing through the front and rear mountingportions 17 d and 17 e of the lower arm 17 is located on the upper sidethan the link support portion 34 b.

As illustrated in FIG. 8B, the upper and lower side members 13 and 14are connected by the rear cross member 12 in the up-down direction, andform a rigid box-shaped structure. Further, the rear-side supportportions 12 b and 12 c of the lower arm 17 are formed on a lower portionof the rear cross member 12 to distribute load of the lower arm 17 inthe front-rear direction via the front and rear mounting portions 17 dand 17 e. Further, the first arm swing centerline L (an imaginary axis)is formed on the upper side than the link support portion 34 b with anangle at which the front and rear mounting portions 17 d and 17 e of thelower arm 17 obtain a recession angle. Thereby, even in a narrow spacesuch that the rear seat pan comes close, it is possible to rigidly formthe lower-arm front-side support portion 35 a and the link supportportion 34 b.

Specifically, it is possible to avoid interference with the toe controllink 20, while enhancing support rigidity by a support portion of thelower arm 17, whereby it is easy to set a recession angle.

As illustrated in FIG. 9 and FIG. 10, the rear cross member 12 forconnecting the upper side member 13 and the lower side member 14 in theup-down direction has a structure of a closed section S4 of a T-shape ina side view, whose size is increased in the vehicle front-rear directionalong an inner lateral surface of the upper side member 13 in thevehicle width direction (in other words, an inner hollow structure of aT-shape in a side view).

As illustrated in FIG. 1 and FIG. 2, the closed section S4 of a T-shapein a side view is formed only on left and right side portions of therear cross member 12. As illustrated in FIG. 8A, a closed section S5extending in the up-down direction and having an I-shape in a side viewis formed on an intermediate portion of the rear cross member 12 in thevehicle width direction. The closed sections S4 and S5 communicate witheach other.

Further, as illustrated in FIG. 9, the lower-arm rear-side supportportions 12 b and 12 c are formed on the lower side of a lateral portionof the rear cross member 12 in the vehicle width direction, which isassociated with the closed section S4 of a T-shape in a side view; andthe rear mounting portion 17 e of the lower arm 17 is supported by thelower-arm rear-side support portions 12 b and 12 c.

The rear cross member 12 including the closed section S4 of a T-shape ina side view includes, on an upper portion thereof, an upper-surfacefront-side projection portion 12 d and an upper-surface rear-sideprojection portion 12 e bulging in the vehicle front-rear direction. Astabilizer support bracket 38 is mounted between the upper-surfacerear-side projection portion 12 e, and the rear-side lower-arm supportportion 12 c (in this embodiment, near the rear-side lower-arm supportportion 12 c) out of the paired front-side and rear-side lower-armrear-side support portions 12 b and 12 c.

As described above, forming the rear cross member 12 into a structure ofthe closed section S4 of a T-shape in a side view makes it possible toincrease the size of a closed section of the rear cross member 12 and toenhance rigidity. Further, mounting the stabilizer support bracket 38between the upper-surface rear-side projection portion 12 e and thelower-arm support portion 12 c of the rear cross member 12 makes itpossible to reinforce the rear cross member 12, and to secure a spacefor installing the stabilizer 25 without increasing the number of parts.

FIG. 13A is a perspective view illustrating the stabilizer supportbracket 38. As illustrated in FIG. 13A, the stabilizer support bracket38 is integrally formed by a pair of inner and outer lateral pieces 38 aand 38 b in the vehicle width direction, and a rear piece 38 c forconnecting the lateral pieces 38 a and 38 b.

The stabilizer 25 is mounted to the rear piece 38 c of the stabilizersupport bracket 38 with use of a support bracket 39, which is fastenedby a bolt and a nut (see FIG. 6 and FIG. 9).

As illustrated in FIG. 1 and FIG. 2, there are formed, on a top portionof the rear cross member 12, a ridge X1 extending in the vehicle widthdirection on an intermediate portion thereof in the vehicle widthdirection, ridges X2 and X2 extending in the vehicle width directionfrom an end of the ridge X1 along an upper end of a front portion of theupper-surface front-side projection portion 12 d, and ridges X3 and X3extending in the vehicle width direction from connection portions of theridges X1 and X2 along an upper end of a rear portion of theupper-surface rear-side projection portion 12 e. The ridges X1, X2, andX3 are combined substantially in an X-shape in a plan view. Thereby,torsional rigidity of the rear cross member 12 is enhanced.

As illustrated in FIG. 9 and FIG. 10, a partition member 40 is providedwithin the closed section S4 in the vicinity of a lower end of thestabilizer support bracket 38 of the rear cross member 12. Alower-portion closed section S6 extending in the vehicle width directionis formed by the partition member 40 and an upper surface of the lowerside member 14.

Forming the lower-portion closed section S6 makes it possible to enhancelocal rigidity of the rear cross member 12 in the vehicle widthdirection, to increase load transmission from the lower-arm rear-sidesupport portions 12 b and 12 c, to prevent sectional deformation byconcentration of stress, and to enhance rigidity in the vehicle widthdirection.

FIG. 12A is a plan view of the partition member 40, and FIG. 12B is aperspective view of the partition member 40. The partition member 40includes a lower piece 40 a located within the closed section S4 of therear cross member 12 and extending in the vehicle width direction, and alateral piece 40 b extending from an outer end of the lower piece 40 ain the vehicle width direction upwardly by a predetermined amountcorresponding to a width of the rear cross member 12 in the front-reardirection, and then, whose sizes of front and rear portions areincreased. The partition member 40 is integrally formed by these pieces40 a and 40 b. As illustrated in FIG. 11, the lower piece 40 a is weldedand fixed to front and rear walls of the rear cross member 12. Asillustrated in FIG. 9, an upper end of the lateral piece 40 b is weldedand fixed to a lower surface of the upper-surface front-side projectionportion 12 d and to a lower surface of the upper-surface rear-sideprojection portion 12 e. The rear cross member 12 may be formed bycombining two members, or may be formed by a hydroformed component.

FIG. 13B is a front view enlargedly illustrating the brace 27. Asillustrated in FIG. 4 and FIG. 13B, the brace 27 includes a middledownwardly bulging portion 27 a bulging downwardly while avoiding thepropeller shaft 26, and a pair of left and right upwardly bulgingportions 27 b and 27 b bulging upwardly on left and right outer sides ofthe middle downwardly bulging portion 27 a in the vehicle widthdirection while avoiding an exhaust pipe 41 (the exhaust pipe 41 isprovided only on the vehicle right side). The brace 27 is integrallyformed by these portions. In this embodiment, the brace 27 isconstituted by an aluminum die cast member.

As illustrated in FIG. 13B, the middle downwardly bulging portion 27 a,and the upwardly bulging portions 27 b and 27 b on the left and rightsides of the middle downwardly bulging portion 27 a overlap each other,and the bulging portions 27 a and 27 b are smoothly and integrallyconnected. As illustrated in FIG. 3, tunnel-portion mounting portions 27c and 27 c extending rearwardly up to the positions of the vehicle-bodymounting portions of the toe control link 20 are integrally formed onlateral portions of the brace 27 in the vehicle width direction.

Further, as illustrated in FIG. 13B, a load transmission path 50 forlinearly connecting the left and right tunnel-portion mounting portions27 c and 27 c in the vehicle width direction is formed in the brace 27.

According to the aforementioned configuration, even in a portion whereit is difficult to dispose a thick brace in a straight manner in thevehicle width direction, it is possible to secure the load transmissionpath 50 for linearly connecting the left and right tunnel-portionmounting portions 27 c and 27 c of the brace 27 in the vehicle widthdirection, while avoiding the propeller shaft 26 and the exhaust pipe41, and to reinforce the brace 27 itself by the bulging portions 27 aand 27 b to thereby reinforce the front cross member 11.

As illustrated in FIG. 4 and FIG. 13B, a differential mount portion 27 dfor supporting a differential mount bush 42 is provided for each of thepaired left and right upwardly bulging portions 27 b of the brace 27.This enables to reinforce the differential mount portion 27 d by theupwardly bulging portion 27 b, and to support a rear differential device(not illustrated) without increasing the number of parts. Thus, it isnot necessary to additionally provide a differential mount bracket onthe front side of the rear differential device.

As illustrated in FIG. 2, a rear differential device (not illustrated)is supported by the differential mount bush 42, and by the differentialmount bracket 29 located on the rear side of the differential mount bush42.

As illustrated in FIG. 3 and FIG. 8B, the brace 27 is connected to thelower side member 14 at a position where the brace 27 overlaps, in abottom view, the lower-arm support portions 32 a and 35 a constituted bya lower portion of the front cross member 11, and the pillar portion 33formed on the rear side of the lower portion of the front cross member11.

Specifically, the tunnel-portion mounting portion 27 c of the brace 27is connected and fixed to a bottom surface of the lower side member 14so as to overlap the lower-arm support portions 32 a and 35 a in abottom view with use of a plurality of fastening members 43 and 43 suchas bolts at a position away from the tunnel-portion mounting portion 27c in the front-rear direction. Thus, the lower-arm support portions 32 aand 35 a are reinforced with use of the brace 27.

In FIG. 1 and FIG. 5, the reference numeral 44 denotes an openingportion for weight reduction. In FIG. 6 and FIG. 7, the referencenumeral 45 denotes an opening portion for use in mounting the mountingportion 17 d of the lower arm 17. In FIG. 8A, the reference numeral 46denotes an arc-shaped recess portion for avoiding interference with aspare tire pan.

As described above, the rear subframe structure of the embodiment is arear subframe structure provided with the rear subframe 10 configuredsuch that the front cross member 11 extending in the vehicle widthdirection, the rear cross member 12 extending in the vehicle widthdirection on the rear side of the front cross member 11, the paired leftand right upper side members 13 extending in the vehicle front-reardirection, and the paired left and right lower side members 14 extendingin the vehicle front-rear direction are connected in a substantiallygrid pattern in a plan view of a vehicle; the vehicle-body mountingportions 15 and 16 formed on both ends of the front cross member 11 inthe vehicle width direction, and on rear ends of the upper side members13, respectively. The front cross member 11 has the closed section S1extending in the vehicle width direction. A left lateral portion and aright lateral portion of the front cross member 11 are inclinedforwardly and downwardly. A front portion of the closed section S1extends downwardly. The lower-arm support portion 32 a is formed on arear portion of the front portion of the closed section S1. The upperside member 13 is connected to a rear surface fan upper portion of theclosed section S1 (see FIG. 2 and FIG. 8B).

According to the aforementioned configuration, forward and downwardinclination of the lateral portion of the front cross member 11 makes itpossible to secure rigidity in the vehicle width direction by downwardenlargement of the front portion of the closed section S1, whileavoiding interference with a rear floor (rear seat pan). Thus, it ispossible to secure rigidity in the vehicle width direction, withoutnarrowing a swing range of the lower arm 17. Further, it is alsopossible to omit a bracket on the front side of the lower-arm supportportion.

In other words, even in a structure configured such that a rear subframeis disposed in a narrow space of a lower portion of a rear seat panwhere it is not possible to connect the front cross member 11 and theside members 13 and 14 with a sufficient closed sectional structure, itis possible to secure high rigidity in the vehicle width direction,while securing a space for a lower-arm support portion by applying theaforementioned configuration.

In the embodiment of the present invention, a recessed portion (see therecessed closed section S1 b) formed by projecting a rear portion (rearsurface) of the closed section S1 upwardly and forwardly is formed inthe lateral portion of the front cross member 11. The second closedsection S3 extending in the vehicle width direction is formed by theclosed section S1 of the lateral portion of the front cross member 11,the vertical wall portion (see the front plate 35) located immediatelyon a rear side of the closed section S1, and the lower side member 14(see FIG. 8B).

According to the aforementioned configuration, it is possible to securea space for supporting the lower arm, while enhancing connectionrigidity of the lower side member 14.

In the embodiment of the present invention, the pillar portion 33 of theclosed sectional structure S2 is formed immediately on the rear side ofthe second closed section S3. The pillar portion 33 including thevertical wall portion (front plate 35) extends upwardly from the lowerside member 14, and is connected to the front cross member 11. A rearsurface of an upper portion of the pillar portion 33 is connected to theupper side member 13 (see FIG. 8B).

According to the aforementioned configuration, a front portion of thelower-arm support portion 32 a is supported by a downwardly extendingportion of the front portion of the closed section S1 of the lateralportion of the front cross member 11. A rear portion of the lower-armsupport portion 35 a is supported by the pillar portion 33 of the closedsectional structure S2. Further, the pillar portion 33 is connected toall of the upper side members 13, the lower side members 14, and thefront cross member 11. This makes it possible to secure high rigidity,while disturbing load.

Further, even if a size in the up-down direction of the recessed portion(recessed closed section S1 b) of the rear portion of the closed section51 is smaller than a size in the up-down direction of the side member 13in order to secure a sufficient space for supporting the lower arm,while lowering the lateral portion of the front cross member 11, it ispossible to enhance connection rigidity by using the pillar portion 33(specifically, the rear plate 34 of the pillar portion 33) as a setplate.

The present invention is not limited only to a configuration of theembodiment.

For example, in the embodiment, an H-shaped lower arm is employed as thelower arm 17. Alternatively, A-shaped lower arm may be employed as thelower arm 17.

The following is a summary of the present invention as described above.

A rear subframe structure according to the present invention is a rearsubframe structure provided with a rear subframe configured such that afront cross member extending in a vehicle width direction, a rear crossmember extending in the vehicle width direction on a rear side of thefront cross member, a pair of left and right upper side membersextending in a vehicle front-rear direction, and a pair of left andright lower side members extending in the vehicle front-rear directionare connected in a substantially grid pattern in a plan view of avehicle; a vehicle-body mounting portion formed on each of both ends ofthe front cross member in the vehicle width direction, and on each ofrear ends of the upper side members; and a lower-arm support portion forsupporting a lower arm. The front cross member has a closed sectionextending in the vehicle width direction, and a front portion of theclosed section extends downwardly by forward and downward inclination ofa left lateral portion and a right lateral portion of the front crossmember. The lower-arm support portion is formed on a lower rear portionof the left lateral portion and the right lateral portion of the frontcross member. The upper side member is connected to an upper rearportion of the left lateral portion and the right lateral portion of thefront cross member.

According to the aforementioned configuration, forward and downwardinclination of the lateral portion of the front cross member makes itpossible to secure rigidity in the vehicle width direction by downwardenlargement of the front portion of the closed section, while avoidinginterference with a rear floor (rear seat pan). Thus, it is possible tosecure rigidity in the vehicle width direction, without narrowing aswing range of the lower arm. Further, it is also possible to omit abracket on the front side of the lower-arm support portion.

In other words, even in a structure configured such that a rear subframeis disposed in a narrow space of a lower portion of a rear seat panwhere it is not possible to connect a front cross member and a sidemember, while securing a sufficient closed sectional structure, it ispossible to secure high rigidity in the vehicle width direction, whilesecuring a space for a lower-arm support portion by applying theaforementioned configuration.

In an aspect of the present invention, when the closed section isdefined as a first closed section, a recessed portion formed byprojecting a rear surface of a lateral portion of the front cross memberupwardly and forwardly is formed in the lateral portion of the frontcross member. The rear subframe includes a vertical wall portion locatedimmediately on a rear side of the lateral portion of the front crossmember. The rear subframe has a second closed section formed by a closedsection of the lateral portion of the front cross member, the verticalwall portion, and the lower side member, and extending in the vehiclewidth direction.

According to the aforementioned configuration, it is possible to securea space for supporting the lower arm, while enhancing connectionrigidity of the lower side member.

In an aspect of the present invention, the rear subframe structurefurther includes a pillar portion of a closed sectional structure havinga part of the vertical wall portion immediately on a rear side of thesecond closed section. The pillar portion extends upwardly from thelower side member and is connected to the front cross member, and a rearsurface of an upper portion of the pillar portion is connected to theupper side member.

According to the aforementioned configuration, a front portion of thelower-arm support portion is supported by a downwardly extending portionof the front portion of the closed section of the lateral portion of thefront cross member. A rear portion of the lower-arm support portion issupported by the pillar portion of a closed sectional structure. Thepillar portion is connected to all of the upper side members, the lowerside members, and the front cross member. This makes it possible tosecure high rigidity, while disturbing load.

Further, even if the thickness of the recessed portion of the rearportion of the closed section is smaller than the thickness of a sidemember in order to secure a sufficient space for supporting the lowerarm, while lowering the lateral portion of the front cross member, it ispossible to enhance connection rigidity by using the pillar portion as aset plate.

INDUSTRIAL APPLICABILITY

As described above, the present invention is advantageously applied to arear subframe structure provided with a rear subframe configured suchthat a front cross member extending in a vehicle width direction, a rearcross member extending in the vehicle width direction on the rear sideof the front cross member, a pair of left and right upper side membersextending in a vehicle front-rear direction, and a pair of left andright lower side members extending in the vehicle front-rear directionare connected in a substantially grid pattern in a plan view of avehicle; and a vehicle-body mounting portion formed on each of both endsof the front cross member in the vehicle width direction, and on each ofrear ends of the upper side members.

1. A rear subframe structure, comprising: a rear subframe configuredsuch that a front cross member extending in a vehicle width direction, arear cross member extending in the vehicle width direction on a rearside of the front cross member, a pair of left and right upper sidemembers extending in a vehicle front-rear direction, and a pair of leftand right lower side members extending in the vehicle front-reardirection are connected in a substantially grid pattern in a plan viewof a vehicle; a vehicle-body mounting portion formed on each of bothends of the front cross member in the vehicle width direction, and oneach of rear ends of the upper side members; and a lower-arm supportportion for supporting a lower arm, wherein the front cross member has aclosed section extending in the vehicle width direction, and a frontportion of the closed section extends downwardly by forward and downwardinclination of a left lateral portion and a right lateral portion of thefront cross member, the lower-arm support portion is formed on a lowerrear portion of the left lateral portion and the right lateral portionof the front cross member, and the upper side member is connected to anupper rear portion of the left lateral portion and the right lateralportion of the front cross member.
 2. The rear subframe structureaccording to claim 1, wherein when the closed section is defined as afirst closed section, a recessed portion formed by projecting a rearsurface of a lateral portion of the front cross member upwardly andrearwardly is formed in the lateral portion of the front cross member,the rear subframe includes a vertical wall portion located immediatelyon a rear side of the lateral portion of the front cross member, and therear subframe has a second closed section formed by a closed section ofthe lateral portion of the front cross member, the vertical wallportion, and the lower side member, and extending in the vehicle widthdirection.
 3. The rear subframe structure according to claim 2, furthercomprising: a pillar portion of a closed sectional structure including apart of the vertical wall portion immediately on a rear side of thesecond closed section, wherein the pillar portion extends upwardly fromthe lower side member and is connected to the front cross member, and arear surface of an upper portion of the pillar portion is connected tothe upper side member.